Speaker
Mr
Shunpei KOYAMA
(Department of Physics, the University of Tokyo)
Description
The highly excited states in weakly bound nuclei have recently been attracting considerable interest. In particular, it is important to reveal states with cluster structure which are expected to appear above particle emission threshold energy. On neutron rich nuclei, for example $^{16}$C, such cluster states could decay into both $\alpha$ emission and multi-neutron emission because the $\alpha$ emission threshold energy ($S_\alpha$) is rather higher than those of neutrons.
States which decay into $\alpha$ + residual are expected to be preferably clustered.
We investigated $\alpha$-cluster states of $^{16}$C by means of invariant mass spectroscopy via $^{12}$Be + $\alpha$ decay channel.
We performed an experiment at SAMURAI magnetic spectrometer[1] in RIBF. Secondary $^{16}$C beam with 200 MeV/nucleon was bombarded on cryogenic liquid helium target[2] with thickness of 150 mg/cm$^2$. $^{16}$C was excited via $\alpha$ inelastic scattering, which is one of the effective reactions to populate cluster states above $S_\alpha$[3].
Reaction residues are momentum analyzed by the SAMURAI spectrometer. Coincidence $\gamma$ rays are also tagged by DALI2 $\gamma$-ray detector array surrounding the target.
Energy levels of $^{16}$C above $S_\alpha$ are reconstructed from four momenta of $^{12}$Be and $\alpha$ residues and detected $\gamma$-ray energy. Several levels are identified. We will report the experimental result and discuss it by comparison with levels given by an AMD calculation[4].
[1] T. Kobayashi, et. al., Nucl. Instr. and Meth. B317 (2013) 294.
[2] M. Kurata-Nishimura, et. al., RIKEN Accel. Prog. Rep. 46 (2013) 165.
[3] T. Kawabata, et. al., Phys. Lett. B 646 (2007) 6.
[4] T. Baba, Y. Chiba and M. Kimura, Phys. Rev. C 90 (2014) 064319.
Primary author
Mr
Shunpei KOYAMA
(Department of Physics, the University of Tokyo)
Co-authors
Alahari Navin
(GANIL, CEA/DSM-CNRS/IN2P3)
Didier Beaumel
(Institut de Physique Nucl’eaire d ’Orsay, IN2P3/CNRS)
Evgenii Nikolskii
(Kurchatov Institute)
Hideaki Otsu
(RIKEN Nishina Center)
Hidetada Baba
(RIKEN Nishina Center)
Hiromi Sato
(RIKEN Nishina Center)
Hiroyoshi Sakurai
(RIKEN Nishina Center)
Hongna Liu
(RIKEN Nishina Center)
Jenny Lee
(RIKEN Nishina Center)
Jongwon Hwang
(Seoul National Univ.)
Julien Gibelin
(LPC CAEN)
Junichi Ohnishi
(RIKEN Nishina Center)
Juzo Zenihiro
(RIKEN Nishina Center)
Ken-ichiro Yoneda
(RIKEN Nishina Center)
Kensuke Kusaka
(RIKEN Nishina Center)
Kimiko Sekiguchi
(Tohoku University)
Masafumi Matsushita
(CNS, the University of Tokyo)
Masaki Sasano
(RIKEN Nishina Center)
Masatoshi Itoh
(CYRIC, Tohoku University)
Megumi Niikura
(the University of Tokyo)
Mizuki Kurata-Nishimura
(RIKEN Nishina Center)
Naoki Fukuda
(RIKEN Nishina Center)
Nobuyuki Chiga
(Tohoku University)
Nobuyuki Kobayashi
(the University of Tokyo)
Noritsugu Nakatsuka
(Kyoto University)
Pieter Doornenbal
(RIKEN Nishina Center)
Satoshi Sakaguchi
(Kyushu University)
Satoshi Takeuchi
(RIKEN Nishina Center)
Sylvain Leblond
(LPC CAEN)
Tadaski Isobe
(RIKEN Nishina Center)
Takahiro Kawabata
(Kyoto University)
Takashi Nanamura
(Tokyo Institute of Technology)
Tetsuya Murakami
(Kyoto University)
Tohru Motobayashi
(RIKEN Nishina Center)
Toshio Kobayashi
(Tohoku University)
Toshiyuki Sumikama
(Tohoku University)
Valerie Lapoux
(Saclay, CEA)
Yasuhiro Togano
(Tokyo Institute of Technology)
Yasunori Wada
(Tohoku University)
Yohei Matsuda
(Kyoto University)
Yohei Shimizu
(RIKEN Nishina Center)
Yoshiteru Satou
(Seoul National Univ.)
Yosuke Kondo
(Tokyo Institute of Technology)
